1. Field of the Invention
This invention relates to the liquid fuel technology, and more particularly to a catalytic liquid fuel added with a catalyst for overcoming problems like low oxidation activity, surface poisoning and fading of the catalysts.
2. Description of the Related Art
The development in human technology has led to a great economical growth, but the accompanying mass production and consumption can't be supported by the recovery capability of the natural environment and result in severe pollution, sharp declines in energy resources and even threats to sustainable development of humans. The hottest issues nowadays include the progressive global warning and depletion of petroleum. To avoid energy crisis caused by insufficient petroleum storage as well as high risk of nuclear cleavage systems and the resulting nuclear waste, all governments in the world are giving every effort to develop more friendly energy technologies. Some alternative energy sources have been provided so far, such as solar cell, wind power generator and fuel cell. All the alternative energy sources not only can replace current electricity generation systems based on petroleum, but also feature low noise and high cleanness in general. Such affinities to the nature are important indicators for the advanced energy utilization of humans in the future.
Among the new energy technologies, the fuel cell is particularly promising. A fuel cell can convert chemical energy directly to electric energy without the limitation of the Carnot cycle to be more efficient in electricity generation than traditional methods, and also has the merits of low noise, low pollution and wide application. Though the fuel cell was initially reported by Grove in 1839, it is firstly applied to the life support systems of the Apollo and Gemini spacecrafts in the 1960's. With the high efficiency and low pollution, the fuel cell has become the most promising energy system in current world where environment protection and energy utilization efficiency are appreciated. The other electricity generation methods, such as waterpower, thermal power, nuclear power, wind power and solar power electricity generations, have respective drawbacks, such as, limitations from the natural conditions (for waterpower, wind power and solar power), pollution (for thermal power) and certain risk (for nuclear power). The fuel used in a fuel cell is traditionally hydrogen, which is oxidized to form water that causes no pollution. Further, since the other electricity generation systems are all centralized ones needing long-range electricity transmission, much energy is lost in the electricity transmission. On the contrary, a fuel cell is a distributed electricity generation system requiring no long-range electricity transmission, and the fuel cell stack can be scaled to satisfy various applications from a 3C product to a community or a large-scale power station. Certain types of fuel cells can also be applied to vehicles to reduce exhausts from the vehicles mainly using gasoline as the fuel, so that the environment is protected and the quality of life is improved.
Among various types of fuel cells, the direct methanol fuel cell (DMFC) is ought to be the most promising one, because methanol is cheaper, safe and easy to store and deliver, and is higher in the electrochemical activity as being an alcohol having the least carbon number. The DMFC was firstly studied in the 1950's, and was practicalized to serve as power sources of lighthouses and rain gauges in the 1970's after the electrodes were modified unceasingly and ion-exchange membranes were developed. In presence of the catalyst on the electrode, methanol is electrochemically reacted and oxidized to CO2 and H2O. Therefore, the DMFC suitably serves as a mobile power source for an electric car or an electric motorcycle, or as a portable power source for a cellular phone or a notebook computer, and has become a trend for future mobile and portable power sources as well as a target of study in many countries.
In a DMFC system, the anode catalyst material usually includes platinum (Pt). However, methanol is incompletely oxidized on platinum at low temperature to produce carbon monoxide (CO), which is adsorbed on the platinum surface to poison the same and reduce its oxidation capability so that the electrochemical performance of the anode material is significantly lowered.
For a platinum catalyst electrode is easily poisoned due to incomplete oxidation of methanol, the development of the platinum-only catalysts is limited. Hence, how to improve the tolerance of the catalyst to carbon monoxide has become a major issue, and many researchers turned to study double-metal catalysts and multi-metal catalysts. However, a double- or multi-metal catalyst suffers from problems like metal dissolution, and is therefore limited in the application.
Conventional fuel cells using a liquid fuel mostly use Pt-catalyst or Pt-catalyst modified by one or more (transition) metals, such as Pt/C, bimetallic catalysts like PtRu/C or PtCo/C or multi-metallic catalysts like PtRuSn, PtRuTi or PtRuMo, or use a transition metal compound to catalyze the liquid fuel and produce an oxidation current. However, these catalysts still suffer from a certain degree of CO-poisoning as well as dissolution of the modifying metal like Ru, Ti, Co, Zn or Mo, so that the catalytic activity ratio of the catalyst is gradually lowered with time.